The present invention concerns direct chill, semi-continuous casting equipment for the manufacture of metal ingots. The metal used is primarily aluminum. The casting equipment includes an upper metal reservoir, a casting mold with an inlet and an outlet, and a moveable base positioned below the outlet with a casting shoe or bottom block which is designed to bear against the outlet at the start of a casting cycle.
In connection with the manufacture of metal castings of small dimensions, for example ingots for extrusion purposes, self-centering casting shoes are used. The arrangement is based on a simple principle in which the casting shoes rest on well-greased bases. The casting dies are fitted with a guide edge which guides each of the casting shoes into place in the dies as the moveable base is moved up. This system functions satisfactorily because of the small dimensions and low weight of the casting shoes.
In connection with roll-ingot casting, however, a similar system will not function satisfactorily because the casting shoe (just one) for this type of casting equipment has a considerably larger bearing surface and is considerably heavier.
In connection with roll-ingot casting it is common to use manual centering of the casting shoe by means of a bar. This results in damage to both the casting shoe and the casting mold as a consequence of the bar, and because the edge of the shoe touches the mold wall. The damage in the form of scratches and cuts on the die wall and casting shoe, respectively can result in surface defects in the roll-ingot workpieces and, in the worst case, in leakage between the casting mold and the casting shoe resulting in damaged workpieces.
Recently, a solution has been introduced in which the casting shoe is stationary, and the casting die or mold is centered around the shoe. The casting mold is thus mounted as a moveable mold and is designed to be moved by means of eight pneumatic cylinders fitted at each of the corners of the mold. As the pneumatic cylinders are operated manually, this solution involves the risk of the edge of the casting shoe damaging the casting mold. In addition, such a solution employing a moveable casting mold and a large number of pneumatic cylinders is very expensive in terms of construction and maintenance.